Dissecar o papel das células imunes na radioresistência dos tumores retais

Despite the plethora of existing rectal cancer (RC) treatment regimens, >50% of the patients present advanced disease at diagnosis and rely, at least once, on radiotherapy (RT) to downstage tumor and improve locoregional control. However, 20-40% of tumors exhibit or DEVELOP RESISTANCE to RT, resulting in high relapse rates and mortality [5,6]. RESISTANCE emerges from a previous FCT-funded exploratory project (READOUT) that started to dissect RC radioresistance using immunospheroids. Under the scope of the MISpheroID consortium, we evidence that these 3D cultures, gathering cancer and immune cells, are excellent biomimetic models for radioresistance studies [7](PR5). Our preliminary results unveiled that immune cells impair RT-induced cell death, sustaining proliferation and orchestrating alterations on iron and lipid metabolic pathways, increasing RC resistance to therapy (PR6,7). Interestingly, we have also reported that the combination of immunomodulatory nanoparticles with RT reeducates murine macrophages and T cells towards a pro-inflammatory response, reducing breast cancer primary tumor growth and lung metastases [8](PR4). Building up on these findings, our HYPOTHESIS is that the immune landscape present at the TME may sustain RADIORESISTANCE mechanisms that impair RT-mediated cell death and support cancer cell survival and immune escape. RESISTANCE overarching goals are to unravel the role of immune cells on RC radioresistance, dissecting the associated MECHANISMS, and identifying novel prognostic BIOMARKERS and potential targets for IMMUNOMODULATORY THERAPIES. This venture profits from emergent single cell resolution and immune mapping techniques to exploit clinical cohorts, comprising tumors exclusively subjected to neoadjuvant short-course radiotherapy (nSCRT), to unveil RC immune-associated RADIORESISTANCE SIGNATURE. This approach will mitigate potential confounding effects caused by other therapies, facilitating a focused comparison between RT responders and non-responders. To tackle this, RESISTANCE embraces four SPECIFIC AIMS to be addressed through interconnected Tasks: 1) Identification and mapping the immune-associated radioresistance signature on a retrospective RC cohort 2) Infer the predictive value of the identified radioresistance signature in the plasma of a prospective RC cohort 3) Dissect the molecular mechanisms underlying immune cells-mediated radioresistance, using 3D biomimetic in vitro models 4) Sensitize tumors to RT through modulation of the radioresistance pathways in an orthotopic mouse model and in human tumor explants Our project will unveil the molecular and IMMUNE LANDSCAPE of radioresistant tumors, decoding the role of immune cells on cancer RADIORESISTANCE and uncovering novel targets for pharmacological intervention. Liquid biopsies from RT-resistant RC patients will be analyzed to infer the relevance of the identified molecules as potential BIOMARKERS for patient stratification at diagnosis. Human 3D biomimetic models will serve as a screening platform for pharmacological inhibitors and assist in dissecting immune-mediated radioresistance mechanisms. Using murine models and patients tumor explants, the most efficient inhibitors that, in combination with RT sensitize tumors, impairing growth and metastases, will be revealed. A PRE-CLINICAL PROOF-OF-CONCEPT that modulation of IMMUNE-MEDIATED RADIORESISTANCE is PARAMOUNT to improve RC patients treatment and survival will be provided